In recent years, the number of electronic devices (i.e., electronicses) mounted on a vehicle or the like is in an increasing trend, and the number of mounted electronic control units (ECUs) as a controller for controlling the electronic devices is also increasing. Thus, a probability that an operational failure occurs in any one of the ECUs is also in an increasing trend.
In particular, when a vehicle system mounted on a vehicle is turned off (that is, when an ignition switch is brought into an off-state), in a case that any one of the ECUs could not transition to a power-saving state (also called a sleep state or the like) due to some defects, a dark current is increased. By this increased dark current, there is a possibility that electric power of an on-vehicle battery is consumed or deterioration of the battery itself is caused, and consequently, there is a possibility that the vehicle may become unable to start.
Also, the “dark current” is for example current that flows in various circuits in a vehicle in a state that an ignition switch is turned off, and it includes a standby current of a microcomputer that constitutes an ECU and the current consumed by a clock, a security system or the like. The dark current in a vehicle is 50 mA or less in general, but in a vehicle that mounts more electric components or the like, there are also ones that consume a larger dark current.
Thus, a conventional example is proposed with respect to a power supply control system that monitors current consumption of each ECU and restrains a dark current by disconnecting the power supply based on the monitoring result or the like (such as JP 2009-081948 A (PTL 1)).
In the conventional power supply control system described in PTL 1, each controller (ECU) self-reports its current value state, and a monitoring device calculates a threshold value based on their total value, and when the threshold value is exceeded, the power supply is disconnected.
More specifically, in a power supply control system 600 of the conventional example, as illustrated in FIG. 5, a plurality of controllers 501A, 501B, and 501C connected to the same power supply line 500 self-report their operation states or allotment threshold current values that conform to their operation states that each grasps to a monitoring device 501E via a communication line 530 as calculation information of a disconnection threshold current value. The monitoring device 501E receives the report, sets the allotment threshold current values for respective controllers 501A, 501B, and 501C, dynamically updates and sets the disconnection threshold current value by using calculated values of these allotment threshold power supply current, and when a power supply output current value exceeds the disconnection threshold current value, a power supply switch 510 on the power supply line 500 is brought into a disconnected state.